1. Field of the Invention
The present invention relates to an optical disk drive, an optical disk, a security control method for an optical disk drive, and a security control program product for an optical disk drive, by which security and accessibility in an optical disk system for optical disks such as a compact disk and a digital versatile disk are improved.
2. Description of the Related Art
In response to increasing demand for larger data recording capacities, such as for motion picture recording, high recording density compact disks (HD-Burn-CDs: High-Density-Burn type) and digital versatile disks (DVDs) are widely used.
For such high capacity memory devices, security-related objectives are to protect against unauthorized tampering with data stored therein and to prevent unauthorized parties from reading the data.
Japanese Patent Laid-Open Publication No. 2001-35092 discloses a technique for improving security of a removable memory such as an optical disk. In this technique, a control area where general users cannot rewrite is pre-allocated in a memory space of a removable memory, and security information such as a user password is recorded in the control area. A user is required to input verification information when accessing the removable memory. A comparison is made between the security information recorded in the control area and the verification information input by the user, and, if a predetermined condition is satisfied, access to the removable memory is allowed.
However, in the above-described conventional technique, a control area to which general users cannot easily make access must be allocated on the removable disk. Because the control area stores control data corresponding to all data to be stored on the removable disk, it is necessary to pre-allocate a considerable memory area as the control area. As a result, there is a significant disadvantage in that the available recording area is reduced.
Furthermore, in the above-described conventional technique, security information corresponding to all data stored on a removable disk is stored collectively in the control area. Therefore, an unauthorized party attempting to read the security information can easily find that information, and thus, with that conventional technique, problems such as leakage and tampering of the security information remain common.
Furthermore, during writing or reading of data, a disk drive head must be frequently moved between the data recording area and the control area on the removable disk. Accordingly, there is a problem in that data access time is increased.